Security ink to stop fake currency notes, illegal drugs

Researchers have synthesised a
light-emitting ink that can be used to develop security codes to stop the production
of fake currencies, illegal drugs and fraudulent copying of vital documents1.

Counterfeiting causes huge
financial losses in the pharmaceutical and financial sectors. Organic dyes and
semiconductor quantum dots are widely used to generate unbreakable security
codes, but dyes are unstable and quantum dots are toxic.

In search of a better security
ink, scientists from the CSIR-National Physical Laboratory (CSIR-NPL) in New
Delhi, led by Bipin Kumar Gupta, prepared a security ink by mixing nanorods of
rare-earth elements with light-emitting solids made of zinc and manganese in a
specific polymer-based ink. They then tested the ink’s potential to check
counterfeiting by printing specific security codes on black paper.

When exposed to ultraviolet
light and infrared laser, the ink emitted yellow and red light. The nanorods
gave off the red light and the light-emitting solids contributed to yellow
emission, indicating that the components of the ink retained their individual
optical properties even in a mixed condition.

The ink was then successfully
used to generate security codes for the national emblem and a logo of a CSIR
institute on black paper, suggesting
its potential for use in combatting fraudulent imitations.

The scientists now plan to make security ink for generating codes for mobile-based
scanners, to provide full protection against counterfeits, says Gupta.